Process of fickling metals



252. COMPOSITIONS,

Patented June 2, 1831 Exam UNITED STATES PATENT OFFICE DEAL H. TOMPKINS, OF NITRO, WEST VIRGINIA, ASSIGNOR TO THE RUBBER SERVICE LABORATORIES COMPANY, OF AKRON, OHIO, A CORPORATION OF OHIO PROCESS OF PICKLING METALS No Drawing.

The present invention relates to the cleaning and preservation of metallic surfaces, wherein the metal is in contact with a. liquid of an acid nature. More particularly, the invention relates to the prevention of excessive pitting and embrittlement of a metal when subjected to a pickling process by treatment with a dilute solution of a non-oxidizing acid.

Certain objects of the present invention are to prevent the acid pickle liquor from attacking clean portions of the surface of ametal; to obviate over-pickling, embrittlement and pitting of the articles treated; to minimize the amount of metal lost in pickling; to increase the efliciency of the pickling operation; to prolong the effective life of the pickling bath; and particularly to facilitate the pickling operation. Other and further objects of the invention will be apparent from the following description and accompanying examples.

I In the art of pickling, the metal is treated with a dilute acid to remove oxides such as rust, scale, and other deposits, after which the metal is preferably washed with water and dipped into an alkaline bath to remove the last traces of free acid. The acid removes the rust and scale, but unfortunately, from the pickling standpoint, unless some agent to prevent such action is present, it attacks the cleaned metal itself, thereby causing loss of metal and producing an evolution of hydrogen gas, which escapes into the air, carrying with it a fine spray of the acid liquor from the pickling bath and producing an atmos phere possessing corrosive properties aind one which is injurious to health and damaging to equipment.

By the present invention, these objectionable features of the pickling process are substantially overcome or reduced to a minimum. To accomplish the objects set forth in accordance with the present invention, there is added to the pickling bath a regulating agent Application filed November 13, 1930. Serial No. 495,519.

The pickle regulator or inhibitor, as disclosed in the present application, comprises an organicacid derivative of a reaction product of sulfui dioxide and an aldehyde-amine reaction product and preferably an organic acid derivative of a reaction product of sulfur dioxide and an aldehyde derivative of a Schiifs base; that is, a product formed by reacting an aldehyde with a Schiffs base, adding sulfur dioxide thereto and treating the product so formed with an organic acid.

In the examples hereinafter set forth of carrying out the metal pickling process, conditions were imposed which duplicated. so far as possible, those commonly followed in commercial practice, so far as concerned acid concentrations and temperatures employed.

Test pieces of 30 gauge low carbon hot rolled steel sheets, approximately 4" x 3" in dimension, were immersed in approximately 640 c. c. of a water solution of sulfuric acid containing approximately 6% by weight of 66 B. acid to which had been added a small quantity of one of the preferred type of inhibitors. The loss in weight of the steel test pieces resulting from maintaining the strips in the pickle bath in the manner described for a definite period of time was then detern 1 ined. The temperature of the pickling bath was maintained at from 176 to 185 F.

(80 to 85 C.) For the acid concentrationof an acid solution of the strength specified above but containing no inhibitor.

One method whereby one of the preferred class of compounds, for example an acetic the weight of the aldehyde-amine product.

Substantially seven-tenths of a molecular proportion of sulfur dioxide was passed thereinto at a rate slow enough for complete absorption and combination to take place while agitating and maintaining a temperature of approximately 30 to 60 C. To the product thus formed, substantially one molecular proportion of acetic acid was added at a temperature of substantially 50 to C. After the addition of the acetic acid was completed, the solvent employed, for example acetone, was removed preferably by evaporation. The product prepared in the manner described, was a resin that was readily soluble in a pickle liquor, as for example dilute sulfuric acid.

A sample of the product prepared as described above was incorporated in a pickling bath in the manner hereinbefore described. Thus, a steel test piece, 3 x 4 in dimension, cut from 30 gauge low carbon hot rolled sheets, exposing approximately 24 square inches of surface and weighing 18.367 grams, was found to lose but 0.248 grams after 40 minutes pickling in 640 c. c. of a 6% sulfuric acid solution containing 0.06 grams of the inhibiting product hereinbefore described. A similar test piece weighing 17.928 grams and treated in the same manner, but without the use of any inhibitor, lost 7.165 grams. Thus it is shown that when an acetic acid derivative of the reaction product of sulfur dioxide and the product formed by reacting substantially three molecular proportions of acetaldehyde and substantially two molecular proportions of aniline is employed as an inhibitor, the loss in weight per square inch of surface exposed corresponds to 0.0103 grams, whereas when no inhibitor is employed in the test described above, the loss per square inch of surface exposed corresponds to 0.2985 grams. The loss in weight per square inch of surface exposed is only 3.5% as great by employing the inhibitor set forth as results if no inhibitor is employed in the pickling process. A greater saving in metal losses results from the use of a larger amount of the inhibitor. Moreover, the steel plates pickled in the presence of the inhibitor set forth are clean and not stained upon removal from the bath.

Other organic acid derivatives of a reaction product of sulfur dioxide and an aldehydeamine, and preferably organic acid derivatives of a reaction product of sulfur dioxide and an aldehyde derivative of a Schiifs base have been prepared in a manner analogous to that hereinbefore set forth, with the exception that the quantity of sulfur dioxide employed in the reaction was substantially one-half a molecular proportion, and the products tested as inhibitors in a pickling bath in the manner hereinbefore described.

Thus, the following organic acid derivatives of sulfur dioxide reaction products of Schiifs bases and of aldehyde derivatives thereof were prepared and the final roducts so obtained employed in a pickling ath and tested in the manner described:

Compound A.-Acetic acid reaction product of the sulfur dioxide derivative of the reaction product of substantially one molecular proportion of beta-naphthylamine and substantially one molecular proportion of formaldehyde.

Compound B.Benzoic acid reaction product of the sulfur dioxide derivative of the reaction product of substantially one molecular proportion of 2,4-diamido diphenylamine and substantially three molecular proportions of heptaldehyde.

Compound C.Benzoic acid reaction product of the sulfur dioxide derivative of the reaction product of substantially two molecular proportions of ortho-toluidine and substantially three molecular proportions of acetaldehyde.

Compound D.Oxalic acid reaction product of the sulfur dioxide derivative of the reaction product of substantially one molecular proportion of aniline and substantially three molecular proportions of heptaldehyde.

Compound E'.Oxalic acid reaction product of the sulfur dioxide derivative of anhydro formaldehyde aniline.

Compocmol F.-Monochloracetic acid reaction product of the sulfur dioxide derivative of the reaction product of substantially one molecular proportion of aniline and substantially one molecular proportion of crotonaldehyde.

Compound G'.Formic acid reaction prod uct of the sulfur dioxide derivative of the reaction product of substantially one molecular proportion of beta-naphthylamine and substantially one molecular proportion of formaldehyde.

Compound H .-Butyric acid reaction product of the sulfur dioxide derivative of the reaction product of substantially one 252. COMPOSITIONS,

The results of tests obtained on immersing steel test strips of 30 gauge low carbon hot rolled sheets, 3" X 4 in dimension for 40 minutes in 640 c. c. of 6% by weight of 66 B. sulfuric acid at 80 C., in the presence of one of the above described inhibitors, are given in Table I.

Table I i v Weight loss Weight Weight of W eight of Inhibiting comof inhisteel strip steel strip g g pound employed bitor embefore after g J g ployed pickling pickling exposed Grams Grams Grams Grams Compound A 0.06 18. 690 18. 580 0. 0046 Compound B 0. 06 18. 142 18.011 0.0055 Compound C 0.06 18. 457 18. 297 0. 0067 Compound D 0.06 18. 311 18. 063 0. 0103 Compound E 0.06 18. 250 17. 849 0. 0167 Compound F 0. 06 18.450 17.060 0. 0579 Compound G 0. 06 18. 228 18. 085 0. 0060 Compound H- 0.06 17. 598 17. 075 0. 0218 None None. 17. 928 10. 763 0. 2985 It is thus apparent from the data set forth that the preferred class of materials constitutes an important and highly efficacious group of inhibitors, as in all cases wherein one of the preferred inhibiting compounds was incorporated in the pickle liquor there resulted a great saving in the loss in weight of the steel test strips that resulted when no inhibitor was employed.

Other examples of the preferred class of compounds have been prepared in a manner analogous to that above described. For example, an acetic acid reaction product of a sulfur dioxide derivative of the reaction product of substantially one molecular proportion of aniline and substantially three molecular proportions of butylaldehyde, a benzoic acid reaction product of a sulfur dioxide derivative of the reaction product of substantially one molecular proportion of ortho-toluidine and substantially three molecular proportions of butylaldehyde, an oxalic acid reaction product of a sulfur dioxide derivative of the reaction product of substantially two molecular proportions of ortho-toluidine and substantially three molecular proportions of acetaldehyde, a salicylic acid reaction procluct of a sulfur dioxide derivative of the reaction product of substantially two molecular proportions of piperidine and substantially one molecular proportion of formaldehyde, a formic acid reaction product of a sulfur dioxide derivative of the reaction product of substantially two molecular proportions of diethylamine and substantially one molecular proportion of formaldehyde, a sulfanilic acid reaction product of a sulfur dioxide derivative of the reaction product of substantially one molecular proportion of propylamine and substantially one molecular proportion of butylaldehyde, and an acetic acid reaction product of a sulfur dioxide derivative of anhydro formaldehyde aniline were prepared and tested in the manner hereinbefore set forth and found to possess the inhibiting qualities of the preferred class of compounds.

It has further been found that other ratios of organic acid, sulfur dioxide and aldehydeainine than those hereinbefore set'forth may be reacted and the reaction products thus obtained employed as inhibitors. Thus, substantially one molecular proportion of the aldehyde derivative of a Schiifs base formed by reacting substantially three molecular proportions of acetaldehyde with substantially two molecular proportions of aniline has been reacted with substantially seven-tenths of a molecular proportion of sulfur dioxide, and the material so prepared further reacted with substantially one-half a molecular proportion of oxalic acid. The compound thus produced was incorporated in a pickle liquor in the manner hereinbefore described, the amount of inhibitor employed and the size and grade of steel sheets used being the same as in the above described tests. A sheet Weighing 18.690 grams was found after pickling 40 minutes to have lost but 0.298 grams or 0.124 grams per square inch of surface exposed. A sheet of the same stock weighing 17.928 grams and treated in the same manner, but with no inhibitor present, suffered a loss of 7.165 grams or 0.2985 grams per square inch of surface exposed.

Although it is desirable that the preferred inhibitor be prepared in the presence of an organic solvent, as for example acetone, ben- Zene and the like, it is not imperative that a solvent be employed. Thus, sulfur dioxide may be reacted with the aldehyde-amine product without dissolving the latter in a solvent, and the product so formed may be further reacted with an organic acid to form a compound of the preferred class and possessing the inhibiting qualities disclosed.

Other modes of employing inhibitors of the class hereinbefore set forth in the acid pickling of metals are apparent to those skilled in the art to which this invention pertains. The products described additionally may be employed in the presence of foaming agents, ioni ble substances or other materials ordinarily used, and are employable with the various acids commonly employed commercially in the acid pickling of metals.

lVhat is claimed is:

1. A process of pickling a metal which comprises subjecting the metal to be pickled to the action of a substantially non-oxidizing mineral acid solution containing a small proportion of an organic acid derivative of a reaction product of sulfur dioxide and an aldehyde-amine product.

2. A process of pickling a metal which comprises subjecting the metal to be pickled to the action of a substantially non-oxidizing mineral acid solution containing a small proportion of an organic acid derivative of a reaction product of sulfur dioxide and an aliphatic aldehyde-aromatic amine reaction product.

3. A process of pickling iron and steel products which comprises subjecting the metal to be pickled to the action of a sulfuric acid solution containing a small proportion of an organic acid derivative of a reaction product of sulfur dioxide and an ald ehyde-amine product.

4. A process of pickling iron and steel products which comprises subjecting the metal to be pickled to the action of a sulfuric acid solution containing a small proportion of an organic acid derivative of a reaction product of sulfur dioxide and an aliphatic aldehyde-aromatic amine product.

5. A process of pickling iron and steel products which comprises subjecting the metal to be pickled to the action of a sulfuric acid solution containing a small proportion of an organic acid derivative of a reaction product of sulfur dioxide and an aldehyde derivative of a Schiffs base.

6. A process of pickling iron and steel products which comprises subjecting the metal to be pickled to the action of a sulfuric acid solution containing a small proportion of an organic acid derivative of a reaction product of sulfur dioxide and an aliphatic aldehyde derivative of a Schiffs base.

7. A process of pickling iron and steel prducts which comprises subjecting the metal to be pickled to the action of a sulfuric acid solution containing a small proportion of an aliphatic acid derivative of a reaction product of sulfur dioxide and an aliphatic aldehyde derivative of a Schiifs base.

8. A process of pickling iron and steel products which comprises subjecting the metal to be pickled to the action of a sulfuric acid solution containing a small proportion of a reaction product of an aliphatic acid containing less than three carbon atoms and a sulfur dioxide derivative of a material formed by reacting an aliphatic aldehyde containing less than eight carbon atoms with a primary aromatic amine.

9. A process of pickling iron and steel products which comprises subjecting the metal to be pickled to the action of a sulfuric acid solution containing a small proportion of an acetic acid derivative of a reaction product of sulfur dioxide and a material formed by reacting substantially three molecular proportions of acetaldehyde with substantially two molecular proportions of aniline.

10. A process of pickling iron and steel products which comprises subjecting the metal to be pickled to the action of a sulfuric acid solution containing a small proportion of a product formed by reacting substantially seven-tenths of a molecular proportion of sulfur dioxide with substantially one molecular proportion of the reaction product of substantially three molecular proportions of acetaldehyde and substantially two molecular proportions of aniline and further reactin the product thus formed with substantiafiy one molecular proportion of acetic acid.

11. A pickling bath for metal products which comprises a substantially non-oxidizing mineral acid solution containing a small proportion of an organic acid derivative of a reaction product of sulfur dioxide and an aldehyde-amine product.

12. A pickling bath for metal products which comprises a substantially non-oxidizing mineral acid solution containing a small proportion of an organic acid derivative of a reaction product of sulfur dioxide and an aliphatic aldehyde-aromatic amine reaction product.

13. A pickling bath for iron and steel products comprising a sulfuric acid solution containing a small proportion of an organic acid derivative of a reaction product of sulfur dioxide and an aldehyde-amine product.

14:. A pickling bath for iron and steel products comprising a sulfuric acid solution containing a small proportion of an organic acid derivative of a reaction product of sulfur dioxide and an aliphatic aldehyde-aroma-tic amine reaction product.

15. A pickling bath for iron and steel products comprising a sulfuric acid solution containing a small proportion of an organic acid derivative of a reaction product of sulfur dioxide and an aldehyde derivative of a Schitfs base.

16. A pickling bath for iron and steel products comprising a sulfuric acid solution containing a small proportion of an organic acid derivative of a reaction product of sulfur dioxide and an aliphatic aldehyde derivative of a Schifls base.

17. A pickling bath for iron and steel products comprising a sulfuric acid solution containing a small proportion of an aliphatic acid derivative of a reaction product of sulfur dioxide and and aliphatic aldehyde derivative of a Schitfs base.

18. A pickling bath for iron and steel products comprising a sulfuric acid solution containing a small proportion of a reaction product of an aliphatic acid containing less than three carbon atoms and a sulfur dioxide derivative of a material formed by reacting an aliphatic aldehyde containing less than eight carbon atoms with a primary aromatic amine.

19. A pickling bath for iron and steel products comprising a sulfuric acid solution containing a small proportion of an acetic acid derivative of a reaction product of sulfur dioxide and a material formed by reacting substantially three molecular proportions 252. COMPOSITIONS,

of acetaldehyde with substantially two molecular proportions of aniline.

20. A pickling bath for iron and steel products comprising a sulfuric acid solution containin a small proportion of a product formed by reacting substantially seventenths of a molecular proportion of sulfur dioxide with substantially one molecular proportion of the reaction product of substantially three molecular proportions of acetaldehyde and substantially two molecu lar proportions of aniline and further reacting the material thus formed with substantially one molecular proportion of acetic acid.

21. A process of pickling iron and steel products which comprises subjecting the metal to be pickled to the action of a sulfuric acid solution containing a small proportion of a product formed by reacting in the presence of acetone substantially seven-tenths of a molecular proportion of sulfur dioxide with substantially one molecular proportion of the reaction product of substantially three molecular proportions of acetaldehyde and substantially two molecular proportions of aniline and further reacting the material thus formed with substantially one molecular proportion of glacial acetic acid.

22. A pickling bath for iron and steel products comprising a sulfuric acid solution containing a small proportion of a product formed by reacting in the presence of acetone substantially seven-tenths of a molecular proportion of sulfur dioxide with substantially one molecular proportion of the reaction product of substantially three molecular proportions of acetaldehyde and substantially two molecular proportions of aniline and further reacting the material thus formed with substantially one molecular proportion of glacial acetic acid.

23. A process of pickling iron and steel products which comprises subjecting the metal to be pickled to the action of a sulfuric acid solution containing a small proportion of a material formed by reacting an organic acid containing less than five carbon atoms with the sulfur dioxide derivative of an aldehyde-amine.

24. A pickling bath for iron and steel products comprising a sulfuric acid solution containing a small proportion of a material formed by reacting an organic acid containing less than five carbon atoms with the sulfur dioxide derivative of an aldehyde-amine.

In testimony whereof I hereunto afiix my signature.

DEAL H. TOMPKINS. 

